The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

1Department of Evolutionary Anthropology, Duke University, 2Department of Anatomy, Kansas City University of Medicine and Biosciences, 3Department of Anthropology, Rutgers, The State University of New Jersey, 4Department of Bioclinical Sciences, Kuwait University

Tufted capuchins employ complex processing behaviors coupled with physical strength to access mechanically-protected foods. It has been argued that tufted capuchins require an extended juvenile period to gain the strength and skill necessary to achieve adult competence when extracting foods embedded in tough or hard tissues. While several behavioral studies have demonstrated that extractive-feeding proficiency improves with age in capuchins, this research has relied on a subjective assessment of dietary mechanical demand. Here we compare the mechanical properties of foods eaten at various stages during tufted capuchin development and examine the relationship between age, feeding behaviors, and food mechanical properties. Our sample included adults (n = 17) and juveniles (n = 11) from two groups of wild tufted capuchins (Cebus libidinosus) at Boa Vista, Brazil. We used continuous focal animal sampling methods to collect data on food processing behaviors. Food mechanical properties were measured using a HKU Darvell universal mechanical tester. Juveniles and adults exploited foods of comparable toughness and Young's modulus (p>0.05). Despite this overlap in food mechanical properties, processing behaviors differed between adults and juveniles when eating certain foods. These results indicate that age-related differences in feeding proficiency are specific to food type and reflect a combination of food mechanics, food geometry, and skill level. These findings emphasize the importance of integrating behavioral and food mechanical property data to better understand the factors influencing the ontogeny of primate feeding.

This study was funded by the NSF-IGERT (DGE 0801634) and the Leakey Foundation.